The internet is bursting at the seams with telescope reviews, which is why I try not to add to that. However, it is harder to find some comprehensive advice regarding what to do when you get that package in the mail, put it together, wait two weeks for the sky to clear (the "curse" of buying a new telescope), and are ready to start observing.
Learning the telescope
Of course you will be eager to start observing, but before you put your new telescope outside under the stars, make sure you read the instructions, whether included with the telescope or found online. Put it together properly and understand what each part does. If you don't, you might end up frustrated that you can't find anything or wondering why everything just looks like a blob.
DO NOT start tweaking collimation, if your telescope allows it, until you know what you are doing. I can't count how many times beginners go online saying they can't see things well in their telescope and because they've heard about collimation they immediately think that's the problem and hopelessly screw up the telescope's alignment. Most telescopes are reasonably well collimated out of the factory and won't be out of alignment so bad that it will even be noticeable to a beginner. They also tend to hold collimation extremely well, so while it's something you will need to learn to do eventually, it's not something I recommend a beginner start messing with. That's a rabbit hole you don't need to go down when you are starting out.
Tripod and/or mount
Steady views are good. Most inexpensive telescopes that beginners buy, except for Dobsonians, tend to be undermounted, giving shaky and frustrating views. That's why advanced amateurs, especially imagers, spend gobs of money on big heavy mounts and tripods. The tripod is the three legged stand that holds the mount, which holds the telescope optical tube assembly (OTA). The mount provides movement in two axes, either in altitude and azimuth or right ascension and declination. Either system allows you to point the telescope tube anywhere in the sky.
Hopefully your telescope's mount is reasonably sturdy. If not, it's not the end of the world. You simply wait a few seconds after touching it (moving the tube to an object, focusing, etc.) for the vibrations to die down. If it's windy and you have a shaky mount, try to get behind a car or the side of a building to minimize the effect. Or just wait until it's not so windy.
Left: The Explore Scientific FirstLight 102mm refractor, with main parts labeled.
A far greater impediment to observing is if the mount is difficult to move smoothly. This is where Dobsonians shine. You simply push the tube where you want it to go. I recommend putting one hand up on the lip of the aperture and the other near the back of the tube. This gives you more precise control and leverage.
Right: A Dobsonian reflector, such as the Apertura AD8, is a simple design that maximizes aperture and stability per dollar spent.
For tripod-mounted scopes, a lower quality mount will really become an issue when you try to move the scope to center an object and track it manually. Some just aren't designed well or are cheaply manufactured, making these operations incredibly frustrating. This is why I like slow motion controls. These are semi-flexible cables with a knob on the end that you turn to allow you to move the scope in finer increments than by just pushing the tube around.
Main optics
Telescopes work by collecting as much light as possible using a larger aperture than the pupil of your eye. Refractors do this using a set of lenses. Reflectors use a large parabolic-shaped mirror. Catadioptrics (Schmidt-Cassegrains, Maksutov-Cassegrains, for example) use a combination of lenses and mirrors to create a light path that folds back upon itself. The larger the aperture, the more light the telescope collects.
By concentrating and focusing this larger amount of collected light into a spot roughly the size of your pupil, a telescope allows you to see dimmer objects and more detail in even bright objects like the Moon or Jupiter. You look through an eyepiece inserted into the telescope where the light comes to focus. The eyepiece contains multiple lenses to magnify the image. In short, the telescope collects and concentrates the light, the eyepiece magnifies it.
Redirecting the light path for comfortable viewing
If you have a refractor or catadioptric ("cat") telescope (like a Schmidt-Cassegrain or a Maksutov-Cassegrain), you will first insert a diagonal, usually containing a mirror tilted at 90 degrees, and insert the eyepiece into that. The diagonal ensures that you have a comfortable position for viewing high up in the sky. If your scope comes with a 90 and and 45 degree diagonal, use the 90 for astronomy and the 45 for terrestrial viewing.
Because the diagonal is usually held in by a couple of thumb screws, you can rotate it to position it more comfortably for viewing. This will change the orientation of the view in the eyepiece, like tilting your head, but you learn to know which way is which after a while. There's no law saying you have to have it set vertically and look straight down into the eyepiece.
A reflector has a diagonal of sorts, too, but it's built into the upper part of the telescope tube. It's called the secondary mirror, and like the mirror diagonal, it's a flat mirror that redirects the focused light path 90 degrees so you can view in a comfortable position, either on the left or right side of the front of the tube.
Generally, a refractor or catadioptric will mirror-reverse the view. A Newtonian reflector will simply rotate it 180 degrees. Understanding directions in your eyepiece will help you make sense out of what you are seeing compared to a chart or image.
Changing magnification
Eyepieces, what some people call "lenses" (or "oculars" for the more esoteric term), are how you change magnification, or power. Except for specific eyepieces with a rotating barrel that actually are zoom lenses, each eyepiece will give you a fixed power depending on its focal length and that of the telescope. You change magnification by changing eyepieces.
The standard eyepiece barrel diameter is 1.25". However, many telescopes have 2" focusers, allowing for larger eyepieces with 2" barrel diameters. Most of these come with a 1.25" adapter so you can use both, or you can buy one.
Magnification (or power) = telescope focal length / eyepiece focal length. So a 750mm focal length telescope with a commonly included 25mm eyepiece will give you 30 power (30x)—magnifying 30 times what your unaided eye sees. Place the eyepiece in the focuser or diagonal, making sure it's seated all the way in, and use the thumbscrews to clamp it tightly so it won't fall out. It doesn't matter how it's rotated.
It's best to remove an eyepiece before you move the telescope to prevent it from falling out if the thumbscrews aren't tight. Get in the habit of frequently checking the tightness of all thumbscrews for eyepieces, diagonals, and finderscopes. After 30+ years with no incident, I recently had an 8x50 finderscope fall from the upright tube of my 10-inch Dobsonian onto the cement floor of the garage. Surprisingly, no damage, but it does happen. (Most finderscopes have a tab on one side of the base of the bracket, however the ones I've seen are always toward the back, where they don't help to prevent the finderscope from sliding out on a reflector, as mine did. Makes more sense to me to have the tab in the front, but it's a refractor thing.)
Taking a seat
Although I stood the first dozen or so years when observing with a telescope, I highly recommend finding a good seat and sitting while you observe. You will be more comfortable, you will get a steadier view, and you won't tire so quickly.
The longer the tube of your telescope, the more variation there will be in the height of the eyepiece as you view objects around the sky. You can get by with a stool or chair for a shorter tube, and for telescopes that use a diagonal you can rotate it to make up some of the difference, but longer tubes such as larger Dobsonians will require an adjustable chair.
You can decide later if you want to spend the money on a commercially available observing chair, such as the
Starbound,
Vestil,
Catsperch, or build your own. Some people also buy and use drum thrones with varying degrees of success.
Right: My homemade Denver Observing Chair that has served me well for over 20 years.
Finding objects
Your telescope should have some sort of finderscope, either what amounts to a tiny refractor mounted on the main scope that magnifies the view or a red dot or red circle finder that projects a dot or circle on a tilted glass or plastic surface and makes it look like the dot is projected onto the sky with no magnification. In either case, it is absolutely critical that you align the finder with the telescope. The finder has a low power (in the case of a red dot, 1x) and wide field so it's easier to find objects than looking directly in the main telescope.
Before searching for anything, focus your finderscope if you have one. This is usually done by loosening a ring near the objective lens and screwing the lens housing in or out, then retightening the ring. Also put your lowest power/widest field eyepiece in the telescope's main focuser and focus on any random stars. Focusing tips are covered later in this article.
Above: Simulated view of the field for the Owl Nebula, M97, in an 8x50 straight-through finderscope on a Dobsonian telescope in a light polluted sky. The view will be rotated 180 degrees from the naked eye view, which matches the view in the eyepiece.
Left: Screenshot from Sky Safari Pro showing the 8x50 field of view, rotated to roughly match the finderscope view above. You can customize the field of view to match your own equipment, which helps to match what the chart is showing to what you are seeing in the finderscope and eyepiece. The small circle around the planetary nebula symbol is the eyepiece filed of view. You can see how much more difficult it is to find something in the eyepiece without first centering it in the finderscope.
Sometimes the labels and other clutter can obscure some of the stars, so be careful. Zoom the screen in and out to see what might be hidden.
Below: Simulated view of the same field for the Owl Nebula, M97, in a red dot finder, also in a light polluted sky. The brightest star in both views is Merak, or Beta Ursae Majoris, magnitude 2.3. The view is the same as your naked eye view, with fewer stars visible than in a magnifying finderscope.
In neither finder will M97 be visible, so you need to aim based on the location in relation to the star patterns from a star chart and what you can see in the sky. Without the magnification of a finderscope, the red dot loses a lot of precision, so it's critical that you use the lowest power/widest field eyepiece that you have once you are pointed in the right general direction.
Sometimes, especially if the object is very dim and you may not recognize it right away, it's better to start by pointing the red dot at the nearest bright star, Merak in this case, then switching to the eyepiece and starhopping your way to the object by comparing the star patterns in your eyepiece to those on the chart. This sounds simple, but it's often difficult to be sure exactly where you are pointing, and it's easy to get lost along the way. It still happens to me all the time. It takes practice and, even with experience, patience.
It's easiest to do the finder rough alignment in the daytime. Find a distant fixed object, like the top of a telephone pole. Put your lowest power eyepiece in (the one with the highest mm number) and center the object in the telescope. Then, without moving where the scope is pointing, look in the finder and use the little thumbscrews on the side of it to put the same object in the center or crosshairs. Do this a couple of times, even using a higher power eyepiece for more accuracy, until you are sure they match.
Each time you go out observing, check the finder alignment on a bright object like the Moon, Jupiter, or a bright star, something you'll be certain you are pointed at. First in the main telescope, then in the finder and adjust the finder as needed. Then when you use the finder to locate an object, it will show up in the main telescope eyepiece. Depending on how accurate the alignment is and how well you positioned the object in the finder, you may need to look around in the main telescope eyepiece a little to find it. Use low power when searching. You can always switch to higher power later.
Some telescopes have a go-to computerized mount, which requires battery power and must be leveled and aligned prior to observing. These aren't as foolproof and simple as they sound, and they often don't work right. They will have tracking, though, which keeps an object more or less centered in the eyepiece. These usually come with a hand controller or are controlled via an app.
Another computerized navigation system is a variation of a push-to configuration, where an app guides you with arrows to manually push the telescope to the location of an object. Again, this must be aligned or calibrated. The Celestron StarSense app is a good example. It takes pictures of the sky and matches them to an internal database. A freeware push-to app is AstroHopper, which requires frequent recalibration but otherwise is a good alternative to pure starhopping or expensive commercial push-to systems.
Focusing
The basic rule for focusing is to slowly turn the focusing knob, or the focuser itself in the case of the helical focuser found on many tabletop telescopes, until the object gets as small and sharp as it can be. If it does so, but then gets larger and fuzzier as you keep turning the knob, then you know where the point of focus was and that you have passed it. Just go back slowly and find it. You may have to tweak the focus in very small increments back and forth until you get the best focus possible for the seeing conditions. Usually you will have to let the scope vibrations settle after each tweak. This is normal unless you have an exceptionally sturdy mount. If your telescope has a dual-speed focuser, you can use the smaller knob for fine focus adjustment, much the same for focusing as slow motion controls on a mount are for centering and tracking objects with more precision.
Stars should look like points in low power. However, in high power, you may begin to see the "
Airy disk," which is the tiny disk of light that the star is spread out into due to the optics in your telescope, its size dependent upon the aperture of your telescope. Dimmer stars will still look like points in high power, but the brighter ones should look like tiny disks surrounded by a thin circle or two, called diffraction rings. This is what you want in a well focused and collimated telescope.
Above: If you look closely, the Airy disks and diffraction rings of the two brightest stars are visible in this simulated high power telescope view. Too often Airy disk images are blown way up in scale so you don't know what you should be seeing.
What if things don't look sharp?
Assuming thin clouds aren't obstructing your view and your focus is the best it can be, then by far and away the likeliest culprit is atmospheric turbulence, or what astronomers call "poor seeing." This is what causes bright stars to "twinkle." The seeing changes based on your location, night to night, and even minute to minute. Some places in the world frequently have very good to excellent seeing, or steadiness. Examples in the United States include much of the western U.S., as well as Florida. The northern, eastern, and midwestern U.S. are often under the jet stream, meaning nights of very good or excellent seeing are rare.
Below: Jupiter and its Galilean moons in good seeing (L) and bad seeing (R). (Jupiter images by TheWitscher via Flickr, CC By 2.0, modified to simulate seeing conditions in eyepiece.)
You'll get used to knowing what's good and bad seeing through experience. When Jupiter, Saturn, or the Moon look like they are sitting in the bottom of a clear flowing stream, you have very poor seeing. Stars will look like undulating blobs. The view will shimmer and boil as waves of thermals pass in the atmosphere. You may not be able to make out a bright star's sharp Airy disk or diffraction ring in high power. Every object will just be a moving mess.
Don't give up just because the seeing isn't great. It's not uncommon to have very brief moments when the air steadies out despite bad seeing. It might only be a split second every few seconds, but you can see a lot in those short bursts of good seeing.
Extended objects like galaxies and nebulae are less obviously affected by seeing, so if you have a very clear night but poor seeing (a common combination), go for those types of objects.
At the other extreme, excellent seeing means you see stars as steady points or Airy disks, bright planets seem to be much larger than you remember and show a lot more detail to an experienced eye. You can see tiny craterlets on the Moon, the shadows are sharply defined with no double-edges, and you see little or no shimmering.
Seeing is also affected by thermal currents within the tubes of some telescopes, mainly reflectors and catadioptrics. Refractors not so much, if at all. This is why you will see some Dobsonian owners with fans installed to blow air through the tube, or "cat" owners who wrap their tubes in Reflectix or other insulating material. It's all to make sure the scope design is not contributing to poor seeing. In the former case, they are trying to cool the mirror down to ambient temperature or remove thermal layers inside the tube. In the latter, they are trying to slow down and distribute the cooling so there are no big temperature differentials or plumes inside the tube to cause poor seeing.
In most cases. setting a reflector or "cat" outside for an hour or so before observing will help, but it's not always possible, given your situation. Just be aware that it may take time for the scope to "settle."
What about collimation?
Rarely is it the case where collimation, the alignment of the telescope's main optics, is so bad that it spoils the view as much as bad seeing. There are tools you can use to check and adjust collimation, but you're better off leaving those alone until you can recognize what is bad seeing versus bad collimation. With bad collimation, you'll often see one side of an object always fuzzier than the other. Stars may look asymmetric, like little bumblebees. On nights of excellent seeing you will still have a "soft" view that you can't quite focus. But don't assume it's bad collimation until you've ruled out bad seeing, poorly made optics, or even the nature of the type of optics.
For example, a "fast" reflector with a small focal ratio, for example f/5, will normally show "coma" at the outer edges of the field, an abberation that makes stars near the edge look like comets. Same with achromat refractors and "chromatic abberation," where you may see blue or yellow color fringing along the edges of bright objects at higher powers, an indication that the focus is going to be a bit soft. These abberations are inherent in the design. Because most everything in life is a compromise.
Learning the sky
Using a telescope is like driving a car. You can learn to drive it, but if you don't know where to go or how to get there it won't do you much good. Even if you have a go-to telescope, the equivalent of an autonomous-driving car, knowing what you want to see, when is a good time to see it, and knowing what to look for are important for enjoying your observing.
Many experienced amateurs recommend buying a book to start learning. That's fine if you are a book-learner, but with so much information available on the internet, with options to ask questions and interact with other people, I wonder if starter books aren't a little obsolete. With younger people especially, I don't think learning from a book is a very appealing process. I think it just depends on the individual.
I did start with some books, but most of my actual learning came from simply getting out and observing, and then reading about the objects I saw. Back then, the charts in the book were most important for me, but with charting apps that's changed. Unlike paper charts, apps are flexible, can be zoomed in and out and filtered and manipulated however you want. So many nights I wished my paper charts went deeper than what they showed. And don't get me started on trying to find the right chart late at night for the area I wanted to observe!
Start with things that are easy to find: the Moon, the bright planets, M42, the Orion Nebula (winter), or M8, the Lagoon Nebula (summer), and brighter star clusters.
We measure the brightness of celestial objects primarily by "magnitude," with higher numbers meaning dimmer, and lower numbers, including negative numbers, meaning brighter. The magnitude scale is reverse logarithmic, therefore a difference of five magnitudes is 100 times brighter or dimmer and each difference of 1 magnitude is about 2.5 times brigher or dimmer.
Venus varies from magnitude -3 to almost -5. The bright star Vega is a reference at magnitude 0.0. The limiting magnitude of the unaided eye (dimmest you can see) in a transparent, dark sky is around magnitude 6 or 7. A typical 3-inch (80mm) telescope can reveal stars to about magnitude 12. A 6-inch (150mm) to about 13.5 magnitude. An 8-inch (200mm) to about magnitude 14. This doesn't sound like much of a difference, but it makes a big difference in what you can see when so many stars and deep sky objects are at these threshold levels for seeing details, or just seeing them at all.
Extended objects like larger nebulas and some more diffuse galaxies will appear dimmer than their listed magnitudes might indicate, in which case we say they have "low surface brightness." This is one of the reasons a larger aperture that collects more light can show many deep sky objects better than smaller ones.
Once you are familiar with using the telescope and have seen some of the brightest objects, observing the rest of the Messier Objects is a good next step. Some of them are more challenging than those in the much larger NGC catalog, but the rest are some of the biggest and brightest. Be realistic in what you try to observe, but once you gain experience, don't be afraid to try for something normally just out of reach if you have a great sky. That's part of the fun of observing!
Navigating the sky
Learn how to navigate with your telescope, depending on what assistive equipment it has. Regardless, learn how to starhop. This means comparing the patterns of the stars you see in your finder or eyepiece with those on a chart and moving the scope to the object you want to see. Unless your go-to or push-to system is really precise and functions flawlessly every time (ha!), you will still need to recognize star patterns and be able to hop to the object from where your navigation system takes you. Knowing how to starhop will also ensure you can continue observing even if your electronic system fails or runs out of power—not an uncommon occurrence.
Observing
Don't expect deep sky objects to look anything like the images you see online or in books. Your eyes, even with the help of a telescope, can't gather as much light or see most of the wavelengths represented in images. So most objects will be white or gray and look rather like dim fuzzy blobs or patches, if you can glimpse them at all. Star clusters on the other hand, at least the ones your telescope can resolve into individual stars, will look like sprinklings of beautiful points.
Once you learn how to observe and spend 10 minutes or more viewing an object, very subtle detail will eventually start to reveal itself on clear and steady nights. Learn to appreciate what you are looking as much as how it looks.
Except when viewing the Moon or bright planets, let your eyes get accustomed to the dark, which takes about 20-30 minutes for full dark adaptation. Use a dim red light when you need light.
As you observe more, you will learn what different objects look like, what to expect, what to look for, and how to improve your observing skills. Astronomerica has articles on using averted vision, understanding distances and directions in the sky, observing the Moon, observing the brighter planets, and observing galaxies, to name a few. The internet has a huge amount of resources.
Modifying and tweaking
Even a high end telescope may require some modification and tweaking by the user, if only to customize it to your own satisfaction. Inexpensive telescopes will almost always require some modifications to get the most out of the equipment, so expect that and don't be afraid to experiment.
Right: I added the right angle bracket and 6x30 finder to my 6-inch tabletop telescope. I also added the light-blocking craft foam, a hose clamp and extra long focuser thumbscrews to improve the helical focuser. These are all reversible mods.
However, don't start making changes until 1) you're sure you are going to keep the telescope, to avoid return or warranty issues, and 2) you've tried it as is and determined there is a modification that you can do yourself that will likely make it better. Mods for specific telescopes are abundantly available online, often offering multiple options to solve common problems. The safest mods are those that can be undone to return the scope to its original condition.
Don't rush to upgrade
Once you're comfortable with all of the above, then you can think about upgrading. Or not. You really don't need a lot of gear to see a lot. You mostly need clear dark skies, good seeing, time, patience, enthusiasm, and experience. You can't buy that.
Unless you are missing a critical piece of gear or it just doesn't work, upgrading equipment should be the last thing on your list. You might find yourself buying a lot of stuff you don't need, won't use, or will have to rebuy once you determine what items you really want or need after observing for a while.
The important thing is to get out under the stars.
